Posted
by
timothy
on Friday April 25, 2014 @11:53AM
from the start-up-and-build-down dept.

the_newsbeagle (2532562) writes "Solar power stations in orbit aren't exactly a new idea — Asimov set one of his stories on such a space station back in 1941. Everyone thinks it's a cool idea to collect solar power 24 hours a day and beam it down to Earth. But what with the expense and difficulty of rocketing up the parts and constructing and operating the stations in orbit, nobody's built one yet. While you probably still shouldn't hold your breath, it's interesting to learn that Japan's space agency has spec'd out such a solar power station."

> What's going to make collecting energy on the ground from a satellite more efficient than collecting it from the sun?

In theory you don't have night, so you get twice as much hours of sunlight. Add "cosine error" and the lack of weather, and you're up to five times.

But then you have to throw away half on the way down to the earth. And then the panels last half as long in space. So in the end it's a *very* small *theoretical* advantage.

Which is, of course, utterly wiped out by the cost of launch. And everyone knows this. But the guys proposing these things are not power companies, but space companies. As is the case here, it's JAXA, the Japanese space agency. Everyone outside the space field is completely aware of the fact that this is an utterly ridiculous idea.

I get how collecting energy in space can be more efficient than collecting it on the ground, but if you actually have to beam it down to earth in the first place, you are going to have to transmit it through the same atmosphere that would reflect and absorb so much of the sun's energy in the first place. Although I can see the theory of not having a night giving additional power, for everything else you are still ending up trying to collect energy on the ground from space, which seems fundamentally no dif

I would not want to be a bird or in an airplane if I passed under this satellite. They'll have to make sure they have some really good fail-safes in place in case it pivots any. I've played SimCity 2000, I've seen what a microwave power plant can do.

I am missing your point. The article does mention using a tether to stabilize the solar array. Are you thinking about electric production? I can be used as such but unfortunately producing electricity robs one of delta, which drops your orbit – eventually into the atmosphere. There is no such thing as a free lunch. Most suggestions I have seen is to pump electricity into the tether to increase delta.

But it might make financial sense for powering McMurdo Base, for instance. The cost of hauling diesel down there is almost as ludicrous. Remote outposts and stuff.

Or if your government decided to send a small team of special forces into hostile territory, that would be a convenient way to provide them power. And you could use "cheap solar power for everyone" as good cover for launching something.

Isn't there a bit of irony in the idea, in a time of global warming attributed to greenhouse capture of solar heat, to capture even more solar energy and send it to earth? A large amount of that energy will be dissipated as heat eventually.

Why I'm bringing it up on Slashdot (aside from the hoped-for karma boost from invoking PC game nostalgia) is that occasional disasters happened if the orbital satellites were ever off by a fraction of a percent and they beamed the energy into the nearby residential population instead.

I'd be very interested to know more details of how they plan to transport the energy to the surface.

In the geostationary orbits there are two periods each year, around March and September, when the satellites are eclipsed by the earth. That's why geostationary satellites need batteries, which are among the heaviest parts of a satellite. And, unfortunately for the power generation idea, these eclipses occur at night for a satellite located above the point it's beaming at.

As for the cost, launching 10,000 tons could be done for something like $50 billion or so. We are talking about a thousand launches, so i

The cost of sending 10 metric tons to LEO and about 5 metric tons to GEO is claimed by SpaceX to be slightly under $60 million USD, or about $6k/kg. That seems to be at least a competitive price (few companies say they can beat SpaceX on launch costs). From this figure, sending 10000 metric tons to GEO would be something like $120 Billion. Some cost savings could definitely happen, although the reusable Falcon 9 with all parts being reused on multiple flights is still about $7 billion each, or dropping that price down to about $14 Billion.

Regardless, a guy who knows the figures for the solar power industry, Elon Musk, who also happens to own a spacecraft launching company as well as a completely separate solar panel manufacturing company (in the form of Solar City) has repeatedly said that spaced based solar power for terrestrial consumers makes absolutely no sense and is something he refuses to become involved with because he thinks it will be a financial disaster if anybody tries to get one going.

It doesn't matter. Even if you could argue that you'd get more energy from an orbital installation, it's still orders of magnitude more expensive than just building more panels on the ground and sticking batteries under them.

You can buy a 1kw solar panel for about $800. It'll weigh about 40 lbs. You can put that same solar panel in orbit, where it will produce twice as much power, for only $48,800. 2x the power for 60x the cost. And that completely ignores the cost of transmitting that power back to earth,

The problem here is that Japan doesn't have any free ground to put that panel on, so you're mainly stuck with covering building rooftops with it. Also, Japan isn't a very sunny place, and has a high latitude. The losses in transmission should be fairly low by using microwaves at a frequency that don't experience much attenuation in the atmosphere (nowhere near as much attenuation as there is for sunlight). Maybe it still doesn't make economic sense even given these factors, but the equation is somewhat d

Japan has tons of free space that they could use for solar. If nothing else, they've got 27,268 kilometers of rail. With an assumption of a 40 foot wide right of way (a very conservative number), that's about 332 square kilometres that they can build solar panels over, giving them (at 5 full-sun-equivalent-hours per day) a theoretical power generation capacity of ~250 gigawatt hours per day. That would be a system capable of delivering an average of a bit more than ten gigawatts of power, a good deal more t

That's a good point. I wonder what the installation costs of that would be, versus the costs of building an orbital facility plus launch costs. (I imagine the ground-based option is far cheaper given current launch costs; eventually, with space elevator tech, the latter might be cheaper.)

Using economics to bash basic science research is ridiculously short-sighted. AT&T refused at first to invest in internet research, because their business model was based on telephones. Business is okay at incremental innovations (making computers smaller), but not at disruptive innovations (making computers in the first place). Research such as this has to be publicly financed, precisely because market signals are too short-sighted and profit-oriented to invest in it.

Errm, it's not short-sighted if the economics will NEVER be feasible. Launch prices will never be low enough that it will be cheaper to put solar panels in orbit and transmit power back to earth, rather than just putting more solar panels (and batteries) on earth in the first place. To do that today, you'd need launch prices that are something like $10 per pound. Even SpaceX is only selling at about $1000 per pound, and even their pie-in-the-sky figures for fully reusable vehicles in the distant future only

I think your "never" is really saying that you don't have the imagination or technical know-how to do it.

Space elevators, for example, could bring down prices. When computers were first invented, who foresaw Moore's law? Yet government investment in the chips that TI produced kept the private sector afloat.

Space elevators are cheap, but they're not free. They'll be very expensive to build, and will only be able to move so much mass at a time, which will result in them having a not insignificant cost to get stuff to GEO. By the time they're practical, the cost of PV panels will have dropped so much that it still will be cheaper to just build more PV panels on earth rather than loft them into orbit on a space elevator.

But that's not a problem we actually have. Baseload power is currently selling for 2 to 3 cents, peak power is up into the 20's. No one is going to build a space-o device to provide something we have trouble giving away.

> cells in space should be more efficient then cells buried underneath the atmosphere

Actually, the opposite is true. Cells, silicon ones anyway, are more efficient under the air. It has to do with their band gap.

> Beaming power to remote locations could be more efficient then hauling fuel

The problem is that all you're doing is replacing the array of solar panels with an array of dipoles. The increase in energy density is about 50%, so you need a field that's almost as big as normal PV. There's really no advantage here.

Your point on base load is a bit off point. Base load is cheap because it uses coal or nuclear. If you want be to carbon neutral or want to close down all of your nuclear plants, those things go away so your cheap base load goes away. And as of today we don’t have any good way to store electricity generated during the day for night time use. Yes – I will acknowledge that there are some interesting projects out there, but nothing cheap enough for prime time today. This would be a solution –

The solar cell problem with efficiency sounds like an issue that might be better addressed by just not using solar cells to directly generate current. How about instead of hoisting heavy PV cells we put up a mirror array built of very thin foil. Arrange the mirrors to direct the light onto a working fluid and generate power using that? The only downside I can think of to that at the moment would be that the mirrors would have to be mechanized to track the sun.

From a Military perspective how to do you keep someone from just shooting down your space based solar array. It's pretty hard to stop a high velocity missile from impacting and destroying a large stationary object this is pretty fragile. I guess you could arm the array with lasers, guns, missiles and such and hope to detect and change the vector of an approaching impactor but that sounds expensive and probably in violation of our no space based weapons treaties. Though the whole array could probably be turn

There are only 3 countries that can shoot down satellites today, the US, China, and Russia. So maybe not against those. I am sure that others could follow suite, but it is going to be a long time before insurgents, irregulars, etc. could do it.

Those are the only thee countries that *HAVE* shot down satellites. In practice, there are others that have the capability. There are other nations with ICBMs and orbital launch capability... and some of those countries are enemies of the US.

Actually, the opposite is true. Cells, silicon ones anyway, are more efficient under the air. It has to do with their band gap.

You're gonna have to explain this more. The atmosphere filters out a good chunk of the spectrum we receive from the sun; if there were truly some benefit to said filtering (which is very suspect) we could simply place a filter in front of the cells.

But for point 2, you are still having to ultimately try to collect that energy on the ground anyways. It would be fine for collecting energy in space that you were using in space, but if you are beaming it to the ground anyways, I really don't see a fundamental difference between that and just collecting it from the sun from the ground.

That said, I can see how it could provide almost 24 hour access to energy (point 1), although I'm not exactly sure that you'd really collect sigificantly more energy doin

Sunlight is broad spectrum and some of it will be absorbed by the atmosphere, clouds, etc..

The idea is to shift the energy from a broad spectrum to a wavelength, like microwaves, which are not absorbed. In theory one can squeeze more energy out. Now, we are talking about sunlight => electricity => microwave output => microwave reception => electricity, so there are known issues that need to be resolved.

First. You can put the satellite so it will always be facing the sun... However, you will need a strip of power receivers that strips across the world. otherwise you will get a large block of rock call the Earth getting in the way of beaming the energy. You may be able to store it then blast it out every day. However energy needs of the world require longer spread out energy. That is why we don't power stuff by lighting.

Second. When you beam the energy back, that energy is going to go threw clouds and

What's going to make collecting energy on the ground from a satellite more efficient than collecting it from the sun?

Probably the ability to do it for more hours than you would have daylight?

If there exists an orbital path which can see the sun 24 hours/day, and that same orbital path lets you see the receiving stations, say, 18 hours/day... you get more access to sunlight than you would otherwise.

Besides, it has the added benefit that if your neighbors get a little uppity, you let your mirrors slide a lit

If there exists an orbital path which can see the sun 24 hours/day, and that same orbital path lets you see the receiving stations, say, 18 hours/day

You can swap those and look for an orbit that can see the receiving station 24 hours/day and the sun more than 18 hours/day. Geostationary orbit would be an option covering both. To not have a period at night, during which you receive no power, you could have two satellites at different points in geostationary orbit pointed at the same receiving station. Then y

Point 1 is moot.... since you are going to try to transmit the energy back down to earth anyways... The atmosphere is going to be just as effective at blocking the energy from the satellites as it is from the sun... possibly even moreso, since the satellites will not actually be transmitting as much energy as the sun can potentially provide.

Point 2 I can see the merit behind... but unless the satellites approach a hundred percent efficiency, I'm still not sure you'd see significant gains over collecti

Nah, we can transmit down from the sat using a different part of the spectrum that the atmosphere is more transparent to.

As to the ground-based receptors - you can, for instance, block microwaves with a mesh that is mostly transparent to visible light. Which means a microwave receptor can be mostly transparent to visible light. Which allows you to use the land under the receptor (if you put it, say, ten feet off the ground) in pretty much any way you desire - grow wheat, corn, cows, etc.

> Nah, we can transmit down from the sat using a different part of the spectrum that the atmosphere is more transparent to.

That's not what he's saying. He's saying that you're more efficiently transmitting a tiny amount of the available power, instead of less efficiently transmitting *all of it*. Unless you propose covering a patch of the sky the same area as the surface of the Earth facing the sun, it is unlikely you will be able to change this.

A satellite in geosynchronous orbit is in daylight essentially 24/7/365. A solar panel on the ground.... isn't.

That being said, this is about as newsworthy as yet another Bennet Hazelton bloviation. Solar power sats have been spec'd out by any number of agencies or organizations with the engineering chops to do so, and they all come a cropper on the same issue - it's simply too goddam expensive to boost the satellite's components into orbit.* Even SpaceX's most fevered dreams of how low they can reduce t

I believe the key difference here is that the soyuz space capsule hasn't killed anyone in 43 years. Which is mildly less impressive than the japanese shinkansen's no passenger fatality record. But more impressive than the shuttle's recent track record.

Pretty soon (for various values of "soon") we're going to need power in space.

NASA is planning asteroid capture. Assuming it goes well and we don't kill ourselves, the next step is to mine the asteroid and use the raw materials to build a bigger Space Station or Lunar Base. Both of which will benefit tremendously from orbital solar platforms.

If we can get some power here on earth in the meantime, all the better.

Pretty soon (for various values of "soon") we're going to need power in space.

That is the reason why the ISS has a 300 kW power supply (essentially similar to the power production of a small municipal power plant for a couple of neighborhoods).

This is also one of the things that anybody talking about space-based solar power singularly refuses to acknowledge, and for reasons I really don't understand other than the insane costs that were involved with installing that much power into space in one place. If you want to understand the challenges and trade-offs of large scale power produ

.... that you can fill with algae and harvest much faster and easier than solar farms not to mention the algae also provide their own energy storage. The algae also can be converted into hydrocarbon chains..... that can in turn make gasoline and other petroleum-based products and fit into the existing energy distribution channels.

First off, Japan is space starved and property prices around it's population centers is staggering. Also, 80% of the country is mountainous.

Second of all, the irradiation in space is higher, about 1.3kw per square meter vs 1kw at the equator.

If you count in the fact that the sun is shining 24 hours a day 365 days a year.. versus the estimated 6 hours a day of good sunshine down on earth, you end up with roughly 5x the light per square meter of collector per hour per day averaged.

I'm not contesing the notion that collecting energy in space is more efficient or that it would save real-estate, or avoid a lot of the problems you find with ground-based collection, but unless you are intending on actually *using* that energy in space, you are still going to have to beam it down to earth in some form. That is going to require ground-based collectors that will use no less real estate than solar collectors, and you'll be dealing with atmospheric efficiency losses anyways. Plus, you'll on

1) In orbit, there's no attenuation of solar energy. On the ground, you have attenuation from the atmosphere, plus the whole problem of there not being any sunlight at night. It's worse in Japan; that country isn't exactly famous for being sunny, despite the flag. It has a high latitude and is pretty rainy as I recall.

2) Japan doesn't have a lot of open area to set up solar panels. Collecting it in orbit and beaming it in concentrated form to

Several giant solar collectors in geosynchronous orbit are beaming microwaves down to the island from 36 000 km above Earth.

What if they miss the aim one day by half a degree — the beam hits outside of whatever is supposed to process it dirtside? What will the effect be — and how far away must that island be located for reasonable level of safety?

When you consider the energy cost of launching the equipment into space (0.5*mass*speed^2) you also find that the system is possibly an energy sink depending on how heavy the equipment is and how efficient your space launch system is. You'd basically need a really good and optimized space elevator to even have a chance at having an energy source.

Every penny of space research that isn't spent towards making space launch cheaper and more efficient should be looked at with some suspicion.

The obvious question is "Why", and that post doesnt really explain its numbers well (though it does some linking). I mean, the equations indicate 40 year lifespan on earth vs 12 in space, but dont give a "why", so Id like to clarify for anyone who is as curious as I was.

The obvious assumption is that earth would be less friendly than space-- you have dust, the atmosphere, weather, etc to deal with, none of which exist in space.

> Oops my badi should have RTFA...i saw the pic and thought they'd be reflecting light

No, you're right, that's definitely what the image implies.

As to the concept of using mirrors, some points

One is that conventional cells max out at about 1.1 "suns", meaning that if you shine more than another 10% light on them you flatline the power. It has to do with the speed of the charge carriers, they can only move so fast and after you get to some point where the incoming photo creates an electron that immediatel

Can't you "disperse" the concentrated light on more panels once it reaches the ground station to avoid the 1.1 "suns" limit? Another way might be to avoid photovoltaic panels and use the concentrated light to boil water.

Sure, but if you're going to shine 1 sun worth of light on the panels, why not just let the sun do it?

> Another way might be to avoid photovoltaic panels and use the concentrated light to boil water

Heat engines of this sort normally max out at about 40%, but given all the losses in this system that's likely not bad at all. There must be something I'm missing about using mirrors, I'll have to look into it more.

It is important to note that the safely limits for microwave radiation is about 10 mW/cm^2. It is widely assumed that this number would be increased for a SPS system, and the baseline figure is 23 mW/cm^2. That compares to about 90 to 110 mW/cm^2 for "bright direct sunlight" under AM1.5 to AM1 conditions.

Let's examine the numbers. The article speaks of a collector "3 kilometres long". Let's assume, for the math, that this is the diameter of

If Japan wants to move away from nuclear power, then space based solar might be the only alternative. Reliance on foreign oil has been a big drain on their economy since shutting down their nuclear power plants after the 2011 Tohoku earthquake and tsunami. The tension with China over the senkaku could be a direct result of increasing pressure to do oil and gas exploration in the surrounding waters. Regardless of Global Climate Change because of burning fossil fuels, we would all be better off if Japan co

You don't need no oil, nor a tokamak coil,Solar stations provide Earth with juice.Power beams are sublime, so nobody will mindIf we cook an occasional goose.

INTERLUDE (to Oh, What A Beautiful Morning)All the cattle are standing like statues.All the cattle are standing like statues.They smell of roast beef every time I ride by,And the hawks and the falcons are dropping like flies...

I've been feeling quite blue since the crystals I grewBecame too big to fit through the door.But from slices I sold, Hewlett-Packard, I'm told,Made a chip that was seven foot four. CHORUS

If we run out of space for our burgeoning raceNo more Lebensraum left for the Mensch,When we're ready to start, we can take Mars apartIf we just find a big enough wrench. CHORUS

I'm sick of this place, it's just McDonald's in spaceAnd living up here is a bore.Tell the shiggies "Don't cry," they can kiss me goodby,'Cause I'm moving next week to L4!

I'm afraid that even if Space X comes to the rescue and gives us a 2-order magnitude (factor of 100) reduction in launch costs it still doesn't make economic sense. As other posters have mentioned, why not just put it on earth? The relative lack of efficiency is more than made up for by not having to pay $$$ per kg to get it into geo-sync orbit. (However a great many cool, exciting and useful things like semi-affordable trips to space for the semi-rich and really good planetary exploration will become po

I'm afraid that even if Space X comes to the rescue and gives us a 2-order magnitude (factor of 100) reduction in launch costs it still doesn't make economic sense. As other posters have mentioned, why not just put it on earth?

It may make economic sense in Japan.

Here's some entertaining statistics: Japan has a population of about 127,000,000, or about 1/3 the United States. All those people live in 152,411 square miles, or a space about the size of Montana.

Imagine land prices in Montana if 1/3 of the population of the US moved there and you might start to get the picture. Remember, these are the people who built an island to put down an airport because there wasn't room.

If you extrapolate the population of Japan out to 2030, you get... about 3.2% less people than today. They have a negative population growth rate.

On top of that, they have tons of usable space for solar: if nothing else, they have a huge amount of rail rights of way that they can put panels over, which gives them several hundred square kilometres of area usable for solar. I did the math in another post, and that alone could supply roughly ten times more power (in watt hours) as their one gigawatt orbital in

It would be super useful for establishing a power network for orbiting stations and possibly future moon bases. If we wanted to do any kind of fabrication in space or on the moon or to provide power for an ion engine we could just attach a microwave receiver to the vessel or station and viola, easy power without all the weight. For any very high energy intensive task you wouldn't need that level of power all the time, so it makes sense to make a dedicated installation for it and be able to beam it where i

How feasible/practical would this be? What would the efficiency be compared to converting sunlight to electricity, then to microwaves at high power (MW? GW? TW?) then having to 'receive' those and convert them to DC power?

Just imagine the massive nuclear power (fission and fusion) infrastructure (including reprocessing) one could construct for the cost of this project. No matter how one looks at it, this kind of space-based PV only gets attention because it seems so cool. In the end we can get a more reliable power infrastructure for less money simply by investing in what is a proven and known to be safe (though not idiot-proof, sadly) technology.

The question is, how much mass would you need to lift to the moon to make mining raw materials and converting it into gigawatts worth of PV panels worth it? Consider also that it's much more expensive to land materials on the moon than it is to get it into geostationary orbit.

The reason is that solar that is on the far side of the planet picking up energy 24x7 can only pick up light that would NEVER have gone to earth. As such, they are now going to beam all sorts of extra energy to the earth to use. It will be realized within 10-20 stations that it is another form of pollution, and a foolish one at that.

OTOH, these would make great sense to use for TEMPORARY situations, such as say the DOD's FOBs (which would normally be powered by diesel that costs from 100-400/gal), or for

While I agree with your comments I do have to point out that it's nice to set goals and to think out of the box when it comes to new ideas. Back in the 1960s we had this President that set a goal for the US in reaching the Moon, which we did. People need goals and objectives to strive for otherwise they become hopeless derelicts like Cliven Bundy. [politico.com]

Really they don't plan to use it a giant space based death that could easily be pointed at North Korea, Shanghai, no its just to beam a metric shit-ton of power to them really, oh the on board missiles and armor plating are just there to keep the space junk from breaking it.